CAA broadband noise prediction for aeroacoustic design

The current status of a hybrid RANS/CAA approach for the simulation of broadband sound generation is presented. The method rests on the use of steady Reynolds Averaged Navier-Stokes (RANS) simulation to prescribe the time-averaged motion of turbulent flow. By means of synthetic turbulence the steady one-point statistics (e.g. turbulent kinetic energy) and turbulent length- and time-scales of RANS are translated into fluctuations of turbulent velocity (or vorticity), whose statistics very accurately reproduce the spatial target distributions of RANS. The synthetic fluctuations are used to prescribe sound sources which drive linear acoustic perturbation equations. The whole approach represents a methodology to solve statistical noise theories with state-of-the-art Computational Aeroacoustics (CAA) tools in the time-domain. A brief overview of the synthetic turbulence model and its numerical discretization in terms of the Random Particle-Mesh (RPM) and Fast Random Particle-Mesh (FRPM) method is given. Results are presented for trailing edge, slat, jet, and combustion noise. Some problems related to the formulation of vortex sound sources are discussed.